Factors associated with poor hip flexion range of motion after total hip arthroplasty in patients with ankylosing spondylitis: a retrospective study on 538 consecutive hips
Bibliographic record
Abstract
BACKGROUND: This study aimed to report the mid-term functional outcomes of total hip arthroplasty (THA) for the treatment of advanced hip involvement in ankylosing spondylitis (AS) and identify the factors associated with poor hip flexion range of motion (ROM) after THA in patients with AS. METHODS: We retrospectively investigated the mid-term functional outcomes in 313 AS patients (538 hips) who underwent primary THA from 2012 to 2017, with a mean follow-up of 7 years (range, 4-9 years). Postoperative functional outcomes were assessed by hip flexion ROM, Harris hip score (HHS), and the Western Ontario and McMaster Universities Arthritis Index (WOMAC). The hips were divided into poor (≤ 90°) and good hip flexion ROM (> 90°) groups based on the degree of hip flexion ROM recorded at the most recent follow-up. We grouped factors related to postoperative hip flexion ROM into three categories: preoperative (or patient-related), intraoperative (or surgery-related), and postoperative factors. Multivariate logistic regression was performed to identify the independent factors associated with postoperative poor hip flexion ROM. RESULTS: The overall flexion-extension ROM improved significantly with a median from 0° (0 ~ 120°) to 100° (30 ~ 130°) after THA (P < 0.001), and the mean HHS increased from 37 to 90 (P < 0.001). There were 102 hips (19%) with a hip flexion ROM of no more than 90°. The poor hip flexion ROM group had significantly lower postoperative HHS and WOMAC than the good hip flexion ROM group (85 ± 6 vs. 91 ± 4, P < 0.001; 63 ± 16 vs. 32 ± 16, P < 0.001). The result of multivariate logistic regression showed that male sex (odds ratio [OR] = 9.42, 95% confidence interval [CI], 1.23 to 72.03), bony ankylosis (OR = 3.02, 95%CI, 1.76 to 5.17), cup anteversion angle (OR = 0.96, 95%CI, 0.93 to 0.98), cup inclination angle (OR = 0.96, 95%CI, 0.93 to 0.99), American Society of Anesthesiologists (ASA) class III (OR = 6.23, 95%CI, 1.83 to 21.70), knee involvement (OR = 7.80, 95%CI, 2.75 to 22.16), and noise (OR = 0.45, 95%CI, 0.25 to 0.81) were independent factors associated with poor hip flexion ROM after THA in patients with AS. CONCLUSION: Nearly one out of the five hips in patients with AS have a poor hip flexion ROM after THA. Care has to be taken in acetabular component positioning during THA and its effect on the postoperative hip flexion function should be considered in the patients. The optimum treatment strategy is that THA should be performed before ankylosis in patients with AS.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".